Porous cross-linked polyimide-urea networks
Porous cross-linked polyimide-urea networks are provided. The networks comprise a subunit comprising two anhydride end-capped polyamic acid oligomers in direct connection via a urea linkage. The oligomers (a) each comprise a repeating unit of a dianhydride and a diamine and a terminal anhydride group and (b) are formulated with 2 to 15 of the repeating units. The subunit was formed by reaction of the diamine and a diisocyanate to form a diamine-urea linkage-diamine group, followed by reaction of the diamine-urea linkage-diamine group with the dianhydride and the diamine to form the subunit. The subunit has been cross-linked via a cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydride groups. The subunit has been chemically imidized to yield the porous cross-linked polyimide-urea network. Also provided are wet gels, aerogels, and thin films comprising the networks, and methods of making the networks.
1. A porous cross-linked polyimide-urea network comprising a subunit comprising two anhydride end-capped polyamic acid oligomers in direct connection via a urea linkage, wherein:
(i) the oligomers (a) each comprise a repeating unit of a dianhydride and a diamine and a terminal anhydride group and (b) are formulated with 2 to 15 of the repeating units;
(ii) the subunit was formed by reaction of the diamine and a diisocyanate to form a diamine-urea linkage-diamine group, followed by reaction of the diamine-urea linkage-diamine group with the dianhydride and the diamine to form the subunit;
(iii) the subunit has been cross-linked via a cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydride groups; and
(iv) the subunit has been chemically imidized to yield the porous cross-linked polyimide-urea network.
2. The network of claim 1 , wherein the dianhydride is selected from the group consisting of benzophenone-3,3′,4,4′-tetracarboxylic dianhydride, 2,2′-bis (3,4′-dicarboxyphenyl) hexafluoropropane dianhydride, and biphenyl-3,3 ′,4,4′-tetracarboxylic dianhydride.
3. The network of claim 1 , wherein the diamine is selected from the group consisting of 2,2′-bis[4-(4-aminophenoxy)phenyl]propane, 3,4′-oxydianiline, 4,4′-oxydianiline, p-phenylene diamine, 2,2′-dimethylbenzidine, bisaniline-p-xylidene, 4,4′-bis(4-aminophenoxy) biphenyl, 3,3‘-bis(4-aminophenoxy)biphenyl, 4,4’-(1, 4-phenylenediisopropylidene)bisaniline, and 4,4′-(1,3-henylenediisopropylidene) bisaniline.
4. The network of claim 1 , wherein the oligomers are formulated with 4 to 9 of the repeating units.
5. The network of claim 1 , wherein the oligomers are formulated with 5 to 7 of the repeating units.
6. The network of claim 1 , wherein the cross-linking agent is selected from the group consisting of a triamine, an aliphatic triamine, an aromatic triamine, 1,3,5-tri(4 -aminophenoxy)benzene, a silica cage structure decorated with three or more amines, octa(aminophenyl)silsesquioxane, octa(aminophenyl)silsesquioxane as a mixture of isomers having the ratio meta:ortho:para of 60:30:10, and para-octa(aminophenyl)silsesquioxane.
7. The network of claim 1 , wherein the subunit has been chemically imidized to completion.
8. A wet gel comprising the network of claim 1 .
9. An aerogel comprising the network of claim 1 .
10. An aerogel comprising the network of claim 1 , wherein the aerogel was obtained by supercritical fluid extraction.
11. An aerogel comprising the network of claim 1 , wherein the aerogel has a density of 0.18 to 0.21 g/cm 3 .
12. An aerogel comprising the network of claim 1 , wherein the aerogel has a porosity of 80 to 90%.
13. An aerogel comprising the network of claim 1 , wherein the aerogel has a Young's modulus of 10 to 40 MPa.
14. An aerogel comprising the network of claim 1 , wherein the weight loss of the aerogel following heating of the network at 310° C. is less than 10%.
15. A thin film comprising the network of claim 1 .
16. A thin film comprising the network of claim 1 , wherein the oligomers are formulated with 5 to 7 of the repeating units.
17. A thin film comprising the network of claim 1 , wherein the thin film has sufficient flexibility to be rolled or folded and then recover completely without cracking or flaking.
18. A thin film comprising the network of claim 1 , wherein the thin film has a tensile strength at yield of 1.0 to 3.5 MPa.
19. A method of making the porous cross-linked polyimide-urea network of claim 1 , the method comprising:
(i) reacting the diamine and the diisocyanate to form the diamine-urea linkage-diamine group;
(ii) reacting the diamine-urea linkage-diamine group with the dianhydride and the diamine to form the subunit;
(iii) cross-linking the subunit with the cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydrides; and
(iv) chemically imidizing the subunit with an imidization catalyst to yield the porous cross-linked polyimide-urea network.
20. The method of claim 19 , wherein the dianhydride is selected from the group consisting of benzophenone-3,3′,4,4′-tetracarboxylic dianhydride, 2,2′-bis (3,4′-dicarboxyphenyl) hexafluoropropane dianhydride, and biphenyl-3,3′,4,4′-tetracarboxylic dianhydride.
21. The method of claim 19 , wherein the diamine is selected from the group consisting of 2,2′-bis[4-(4-aminophenoxy)phenyl]propane, 3,4′-oxydianiline, 4,4′-oxydianiline, p-phenylene diamine, 2,2′-dimethylbenzidine, bisaniline-p-xylidene, 4,4′-bis(4-aminophenoxy)biphenyl, 3,3′-bis(4-aminophenoxy)biphenyl, 4,4′-(1,4-phenylenediisopropylidene)bisaniline, and 4,4′-(1,3-phenylenediisopropylidene)bisaniline.
22. The method of claim 19 , wherein the oligomers are formulated with 4 to 9 of the repeating units.
23. The method of claim 19 , wherein the oligomers are formulated with 5 to 7 of the repeating units.
24. The method of claim 19 , wherein the cross-linking agent is selected from the group consisting of a triamine, an aliphatic triamine, an aromatic triamine, 1,3,5-tri(4-aminophenoxy) benzene, a silica cage structure decorated with three or more amines, octa(aminophenyl)silsesquioxane, octa(aminophenyl)silsesquioxane as a mixture of isomers having the ratio meta:ortho:para of 60:30:10, and para-octa(aminophenyl)silsesquioxane.
25. The method of claim 19 , wherein the subunit has been chemically imidized to completion.
26. The method of claim 19 , wherein the imidization catalyst comprises acetic anhydride and pyridine.
27. A porous cross-linked polyimide-urea aerogel comprising a cross-linked and imidized subunit comprising two anhydride end-capped polyamic acid oligomers in direct connection via a urea linkage, wherein the oligomers (a) each comprise a repeating unit of a dianhydride and a diamine and a terminal anhydride group and (b) are formulated with 2 to 15 of the repeating units, and the aerogel has a density of 0.18 to 0.21 g/cm 3 and a Young's modulus of 10 to 40 MPa.
28. The aerogel of claim 27 , wherein the dianhydride is benzophenone-3,3′, 4,4′-tetracarboxylic dianhydride, and the diamine is 2,2′-bis[4-(4-aminophenoxy)phenyl]propane.
29. The aerogel of claim 27 , wherein the aerogel has a porosity of 80 to 90%.
30. The aerogel of claim 27 , wherein the aerogel has a BET surface area of 350 to 500 m 2 /g.
31. The aerogel of claim 27 , wherein the weight loss of the aerogel following heating of the network at 310° C. is less than 10%.
32. A thin film comprising the aerogel of claim 27 .
33. The thin film of claim 32 , wherein the thin film has sufficient flexibility to be rolled or folded and then recover completely without cracking or flaking.
34. The thin film of claim 32 , wherein the thin film has a tensile strength at yield of 1.0 to 3.5 MPa.